Metalloproteases and inhibitors in arthritic diseases

Inflammatory cytokines IL-32 and IL-17 have common signaling intermediates despite differential dependence on TNF-receptor 1

Cytokines IL-32 and IL-17 are emerging as critical players in the pathophysiology of immune-mediated chronic inflammatory diseases. It has been speculated that the molecular mechanisms governing IL-32- and IL-17-mediated cellular responses are differentially dependent on the TNF pathway. In this study, kinome analysis demonstrated that following stimulation with cytokine IL-32, but not IL-17, there was increased phosphorylation of a peptide target corresponding to TNF-R1. Consistent with this observation, blocking TNF-R1 resulted in a suppression of IL-32-induced downstream responses, indicating that IL-32-mediated activity may be dependent on TNF-R1. In contrast, blocking TNF-R1 did not affect IL-17-induced downstream responses. Kinome analysis also implicated p300 (transcriptional coactivator) and death-associated protein kinase-1 (DAPK-1) as signaling intermediates for both IL-32 and IL-17. Phosphorylation of p300 and DAPK-1 upon stimulation with either IL-32 or IL-17 was confirmed by immunoblots. The presence of common targets was supported by results demonstrating similar downstream responses induced in the presence of IL-32 and IL-17, such as transcriptional responses and the direct activation of NF-κB. Furthermore, knockdown of p300 and DAPK-1 altered downstream responses induced by IL-32 and IL-17, and impacted certain cellular responses induced by TNF-α and IL-1β. We hypothesize that p300 and DAPK-1 represent nodes where the inflammatory networks of IL-32 and IL-17 overlap, and that these proteins would affect both TNF-R1-dependent and -independent pathways. Therefore, p300 and DAPK-1 are viable potential therapeutic targets for chronic inflammatory diseases.

Divergent upstream osteogenic events contribute to the differential modulation of MG63 cell osteoblast differentiation by MMP-1 (collagenase-1) and MMP-13 (collagenase-3)

Previously we showed that MMP-1 (collagenase-1) and MMP-13 (collagenase-3) differentially regulate the expression of osteoblastic markers in a heterogenous population of primary human periodontal ligament cells. The mechanisms for these differential responses are not known, but may result from divergence in regulation of early osteogenic transcription factors. The purpose of this study was to elucidate where in the hierarchy of osteoblast-specific transcription factors and markers the differences in MMP-1- and -13-mediated regulation of osteoblastic differentiation arise. We found that the overexpression of MMP-1 resulted in significant decreases in BMP-2, Dlx5, AP, OP and BSP and increases in TGF-β1 and MSX2. In contrast, MMP-13 overexpression resulted in significant decreases in Runx2, OP and BSP, and increases in TGF-β1, MSX2 and OC. The knockdown of MMP-1 caused significant increases in all osteoblastic markers. MMP-13 knockdown produced significant increases only in TGF-β1, MSX2 and Osx, but decreases in Runx2 and OC. Suppression of both MMPs together resulted in significant increases of all osteoblastic markers except Runx2. MMP-1 had a more robust and generalized effect in regulating osteoblast transcription factors and markers than MMP-13. Finally, of the markers and transcription factors assayed, Runx2 is the most early stage transcription factor induced by suppression of MMP-1, while Osx and MSX2 are the most early stage transcription factors regulated by MMP-13. These data show that MMP-1's and -13's differential regulation of osteoblastic markers in MG63 cells likely results from their modulation of divergent signaling pathways involved in osteoblastic differentiation.

Thymoquinone inhibits matrix metalloproteinase expression in rabbit chondrocytes and cartilage in experimental osteoarthritis

Thymoquinone (TQ) is the main constituent of Nigella sativa oil, which has been traditionally used against arthritis in the Middle East. In this study, we investigated the effect of TQ against matrix metalloproteinase (MMP) expression in both rabbit chondrocytes and animal mode of osteoarthritis (OA) induced by anterior cruciate ligament transection and tested whether or not nuclear factor kappa B (NF- κB) was involved in this process. TQ down-regulated MMP-1, MMP-3 and MMP-13 expression and up-regulated tissue inhibitors of metalloproteinase-1 expression as assessed by quantitative realtime polymerase chain reaction. In addition, NF- κB p65 protein level as well as its translocation induced by interleukin-1 β were inhibited by TQ. Our findings suggest the potential of TQ in the treatment of OA.

Proximal interphalangeal joint arthritis

Proximal interphalangeal joint function is critical for proper finger and hand function and arthritis of this joint can lead to considerable hand impairment. Proximal interphalangeal joint arthritides are broadly categorized into nonerosive and erosive osteoarthritis (OA), posttraumatic arthritis, and inflammatory arthritis. The nonerosive type is considered idiopathic or primary OA, whereas the erosive form exhibits an inflammatory component. Idiopathic or primary OA occurs as a consequence of abnormal mechanical stress that leads to damage of cartilage and subchondral bone, with subsequent cytokine and growth factor activation. Individual genetics then mediate the cellular responses. Although erosive OA is described as a separate entity, this remains controversial, with many suggesting that it is merely a more aggressive form of nonerosive, primary OA. Inflammatory OA occurs when connective tissues are diseased, allowing for normal use to incite arthritic damage. Treatment modalities for proximal interphalangeal joint arthritis are currently limited.

Cartilage biology, pathology, and repair

Osteoarthritis is one of the most common forms of musculoskeletal disease and the most prominent type of arthritis encountered in all countries. Although great efforts have been made to investigate cartilage biology and osteoarthritis pathology, the treatment has lagged behind that of other arthritides, as there is a lack of effective disease-modifying therapies. Numerous approaches for dealing with cartilage degradation have been tried, but enjoyed very little success to develop approved OA treatments with not only symptomatic improvement but also structure-modifying effect. In this review we discuss the most recent findings regarding the regulation of cartilage biology and pathology and highlight their potential therapeutic values.

Granulocyte-macrophage colony-stimulating factor- and tumor necrosis factor alpha-mediated matrix metalloproteinase production by human osteoblasts and monocytes after infection with Brucella abortus

Osteoarticular complications are common in human brucellosis, but the pathogenic mechanisms involved are largely unknown. Since matrix metalloproteinases (MMPs) are involved in joint and bone damage in inflammatory and infectious diseases, we investigated the production of MMPs by human osteoblasts and monocytes, either upon Brucella abortus infection or upon reciprocal stimulation with factors produced by each infected cell type. B. abortus infection of the normal human osteoblastic cell line hFOB 1.19 triggered a significant release of MMP-2, which was mediated in part by granulocyte-macrophage colony-stimulating factor (GM-CSF) acting on these same cells. Supernatants from infected osteoblasts exhibited increased levels of monocyte chemoattractant protein 1 and induced the migration of human monocytes (THP-1 cell line). Infection with B. abortus induced a high MMP-9 secretion in monocytes, which was also induced by heat-killed B. abortus and by the Omp19 lipoprotein from B. abortus. These effects were mediated by Toll-like receptor 2 and by the action of tumor necrosis factor alpha (TNF-α) produced by these same cells. Supernatants from B. abortus-infected monocytes induced MMP-2 secretion in uninfected osteoblasts, and this effect was mediated by TNF-α. Similarly, supernatants from infected osteoblasts induced MMP-9 secretion in uninfected monocytes. This effect was mediated by GM-CSF, which induced TNF-α production by monocytes, which in turn induced MMP-9 in these cells. These results suggest that MMPs could be potentially involved in the tissue damage observed in osteoarticular brucellosis.

Anti-arthritic effects of chlorogenic acid in interleukin-1β-induced rabbit chondrocytes and a rabbit osteoarthritis model

Cartilage degradation is one of the pathological changes of osteoarthritis (OA), and accumulating evidence suggests an excess of matrix metalloproteinases (MMPs) plays a role in this cartilage breakdown. Here, we investigated the effects of chlorogenic acid (CGA) on the mRNA and protein expression of MMPs in interleukin (IL)-1β-induced rabbit chondrocytes and evaluated the in vivo effects of CGA in experimental OA induced by anterior cruciate ligament transection (ACLT) in rabbits. Using quantitative real-time PCR and ELISA to investigate the expression levels of MMP-1, MMP-3, MMP-13, and tissue inhibitors of metalloproteinase-1(TIMP-1) in IL-1β-induced rabbit chondrocytes, we showed that CGA inhibits the expression of these MMPs while increasing TIMP-1 expression, at both the mRNA and protein levels. In addition, IL-1β-induced activation of nuclear factor kappa B (NF-κB) and the degradation of inhibitor of κB (IκB)-α were suppressed by CGA. In rabbits, CGA decreased cartilage degradation as assessed by morphological and histological analyses. The down-regulation of MMP-1, MMP-3, and MMP-13 expression and up-regulation of TIMP-1 expression were also detected in CGA-treated cartilage compared with vehicle-treated cartilage, confirming these findings in an in vivo model. Taken together, these findings indicate that CGA may be considered as a possible candidate agent in the treatment of OA.

Orally active MMP-1 sparing α-tetrahydropyranyl and α-piperidinyl sulfone matrix metalloproteinase (MMP) inhibitors with efficacy in cancer, arthritis, and cardiovascular disease

α-Sulfone-α-piperidine and α-tetrahydropyranyl hydroxamates were explored that are potent inhibitors of MMP's-2, -9, and -13 that spare MMP-1, with oral efficacy in inhibiting tumor growth in mice and left-ventricular hypertrophy in rats and in the bovine cartilage degradation ex vivo explant system. α-Piperidine 19v (SC-78080/SD-2590) was selected for development toward the initial indication of cancer, while α-piperidine and α-tetrahydropyranyl hydroxamates 19w (SC-77964) and 9i (SC-77774), respectively, were identified as backup compounds.

Urokinase plasminogen activator receptor and/or matrix metalloproteinase-9 inhibition induces apoptosis signaling through lipid rafts in glioblastoma xenograft cells

Small interfering RNA (siRNA)-mediated transcriptional knockdown of urokinase plasminogen activator receptor (uPAR) and matrix metalloproteinase-9 (MMP-9), alone or in combination, inhibits uPAR and/or MMP-9 expression and induces apoptosis in the human glioblastoma xenograft cell lines 4910 and 5310. siRNA against uPAR (pU-Si), MMP-9 (pM-Si), or both (pUM-Si) induced apoptosis and was associated with the cleavage of caspase-8, caspase-3, and poly(ADP-ribose) polymerase. Furthermore, protein levels of the Fas receptor (APO-1/CD-95) were increased following transcriptional inactivation of uPAR and/or MMP-9. In addition, Fas siRNA against the Fas death receptor blocked apoptosis induced by pU-Si, pM-Si, or pUM-Si, thereby indicating the role for Fas signaling in pU-Si-, pM-Si-, or pUM-Si-mediated apoptotic cell death of human glioma xenograft cells. Thus, transcriptional inactivation of uPAR and/or MMP-9 enhanced localization of Fas death receptor, Fas-associated death domain-containing protein, and procaspase-8 into lipid rafts. Additionally, disruption of lipid rafts with methyl β cyclodextrin prevented Fas clustering and pU-Si-, pM-Si-, or pUM-Si-induced apoptosis, which is indicative of coclustering of Fas death receptor into lipid rafts in the glioblastoma xenograft cell lines 4910 and 5310. These data indicate the crucial role of the clusters of apoptotic signaling molecule-enriched rafts in programmed cell death, acting as concentrators of death receptors and downstream signaling molecules, and as the linchpin from which a potent death signal is launched in uPAR- and/or MMP-9-downregulated cells.

Serum TGF-beta2 and TGF-beta3 are increased and positively correlated to pain, functionality, and radiographic staging in osteoarthritis

The goal of this study was to verify or reject the hypothesis that systematic differences exist in various profibrotic or antifibrotic factors between osteoarthritic patients and controls, as well as between different stages of osteoarthritis. The study group comprised 63 patients with knee osteoarthritis and 18 controls. Transforming growth factor-beta (TGF-beta)1, -2, -3; tissue inhibitor of metalloproteinase (TIMP)-1 protein levels; and gelatinolytic activity of matrix metalloproteinase (MMP)-1, -2, -3, -9 activities were measured by enzyme-linked immunosorbent assay and gelatin zymography, respectively. Visual analog scale scores, Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores, Lequesne clinical osteoarthritis scales, and Kellgren-Lawrence radiographic grading were recorded for each patient.Transforming growth factor-beta2 and -3 (in contrast to TGF-beta1 and TIMP-1) serum protein levels were significantly higher in osteoarthritic patients compared to controls (210%+/-14% [P<.001] and 232%+/-7% [P<10(-7)], respectively). Additionally, TGF-beta2 and -3 were strongly positively correlated to Kellgren-Lawrence radiographic grading of the disease (P<10(-5) and P<10(-7), respectively). Moreover, TGF-beta2 correlated positively with the WOMAC scale (P=.007). However, TIMP-1 decreased as osteoarthritis progressed clinically, but remained irrelevant to radiographic staging. Furthermore, activities of MMP-2 and -9, but not MMP-1+/-3, were lower in patients with osteoarthritis.

A disintegrin and metalloproteinase with thrombospondin motifs 9 (ADAMTS9) expression by chondrocytes during endochondral ossification

A disintegrin and metalloproteinase with thrombospondin motifs 9 (ADAMTS9) is known to influence aggrecan degradation in endochondral ossification, but its role has not been well understood. In the present study, in vitro gene expression of ADAMTS9 was investigated by RT-PCR in ATDC5 cells in which experimentally chondrogenic differentiation had been induced. We also investigated the protein localization and gene expression pattern of ADAMTS9 in the tibia growth plate cartilage of male mice in a day 1 neonate, 7-week-old young adult, and a 12-week-old adult by immunohistochemistry and in situ hybridization and compared the results with the expression of proliferating cell nuclear antigen (PCNA) and type X collagen for the identification of proliferative and hypertrophic chondrocyte phenotypes, respectively. We found the gene expression of ADAMTS9 by ATDC5 cells as a dual mode, both before the expression of type X collagen and after hypertrophic differentiation. The immunoreactivity of ADAMTS9 was observed in chondrocytes of proliferative and hypertrophic zones in the growth plate. The population of ADAMTS9 positive cells decreased with age. The results of the present study suggest that ADAMTS9 might have a role in aggrecan cleavage around the chondrocytes to allow chondrocyte proliferation and hypertrophy.

SirT1 enhances survival of human osteoarthritic chondrocytes by repressing protein tyrosine phosphatase 1B and activating the insulin-like growth factor receptor pathway

OBJECTIVE

The protein deacetylase SirT1 inhibits apoptosis in a variety of cell systems by distinct mechanisms, yet its role in chondrocyte death has not been explored. We undertook the present study to assess the role of SirT1 in the survival of osteoarthritic (OA) chondrocytes in humans.

METHODS

SirT1, protein tyrosine phosphatase 1B (PTP1B), and PTP1B mutant expression plasmids as well as SirT1 small interfering RNA (siRNA) and PTP1B siRNA were transfected into primary human chondrocytes. Levels of apoptosis were determined using flow cytometry, and activation of components of the insulin-like growth factor receptor (IGFR)/Akt pathway was assessed using immunoblotting. OA and normal knee cartilage samples were subjected to immunohistochemical analysis.

RESULTS

Expression of SirT1 in chondrocytes led to increased chondrocyte survival in either the presence or the absence of tumor necrosis factor alpha/actinomycin D, while a reduction of SirT1 by siRNA led to increased chondrocyte apoptosis. Expression of SirT1 in chondrocytes led to activation of IGFR and the downstream kinases phosphatidylinositol 3-kinase, phosphoinosite-dependent protein kinase 1, mTOR, and Akt, which in turn phosphorylated MDM2, inhibited p53, and blocked apoptosis. Activation of IGFR occurs at least in part via SirT1-mediated repression of PTP1B. Expression of PTP1B in chondrocytes increased apoptosis and reduced IGFR phosphorylation, while down-regulation of PTP1B by siRNA significantly decreased apoptosis. Examination of cartilage from normal donors and OA patients revealed that PTP1B levels are elevated in OA cartilage in which SirT1 levels are decreased.

CONCLUSION

For the first time, it has been demonstrated that SirT1 is a mediator of human chondrocyte survival via down-regulation of PTP1B, a potent proapoptotic protein that is elevated in OA cartilage.

The role of ADAMTSs in arthritis

The ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family consists of 19 proteases. These enzymes are known to play important roles in development, angiogenesis and coagulation; dysregulation and mutation of these enzymes have been implicated in many disease processes, such as inflammation, cancer, arthritis and atherosclerosis. This review briefly summarizes the structural organization and functional roles of ADAMTSs in normal and pathological conditions, focusing on members that are known to be involved in the degradation of extracellular matrix and loss of cartilage in arthritis, including the aggrecanases (ADAMTS-4 and ADAMTS-5), ADAMTS-7 and ADAMTS-12, the latter two are associated with cartilage oligomeric matrix protein (COMP), a component of the cartilage extracellular matrix (ECM). We will discuss the expression pattern and the regulation of these metalloproteinases at multiple levels, including their interaction with substrates, induction by pro-inflammatory cytokines, protein processing, inhibition (e.g., TIMP-3, alpha-2-macroglobulin, GEP), and activation (e.g., syndecan-4, PACE-4).

Matrix metalloproteinase and G protein coupled receptors: co-conspirators in the pathogenesis of autoimmune disease and cancer

Similarities in the pathologies of autoimmune diseases and cancer have been noted for at least 30 years. Inflammatory cytokines and growth factors mediate cell proliferation, and proteinases, especially the collagenase, Matrix Metalloproteinase-1 (MMP-1), contribute to disease progression by remodeling the extracellular matrix and modulating the microenvironment. This review focuses on two cancers (melanoma and breast) and on the autoimmune disorder, rheumatoid arthritis (RA), and discusses the activated stromal cells found in these diseases. MMP-1 was originally thought to function only to degrade interstitial collagens, but recent studies have revealed novel roles for MMP-1 involving the G protein-coupled receptors: the chemokine receptor, CXCR-4, and Protease Activated Receptor-1 (PAR-1). Cooperativity between MMP-1 and CXCR4/SDF-1 signaling influences the behavior of activated fibroblasts in both RA and cancer. Further, MMP-1 is a vital part of an autocrine/paracrine MMP-1/PAR-1 signal transduction axis, a function that amplifies its potential to remodel the matrix and to modify cell behavior. Finally, new therapeutic agents directed at MMP-1 and G protein-coupled receptors are emerging. Even though these agents are more specific in their targets than past therapies, these targets are often shared between RA and cancer, underscoring fundamental similarities between autoimmune disorders and some cancers.

The emerging roles of ADAMTS-7 and ADAMTS-12 matrix metalloproteinases

The a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) comprise a family of secreted zinc metalloproteinases with a precisely ordered modular organization. These enzymes play an important role in the turnover of extracellular matrix proteins in various tissues and their dysregulation has been implicated in disease-related processes such as arthritis, atherosclerosis, cancer, and inflammation. ADAMTS-7 and ADAMTS-12 share a similar domain organization to each other and form a subgroup within the ADAMTS family. Emerging evidence suggests that ADAMTS-7 and ADAMTS-12 may play an important role in the development and pathogenesis of various kinds of diseases. In this review, we summarize what is currently known about the roles of these two metalloproteinases, with a special focus on their involvement in chondrogenesis, endochondral ossification, and the pathogenesis of arthritis, atherosclerosis, and cancer. The future study of ADAMTS-7 and ADAMTS-12, as well as the molecules with which they interact, will help us to better understand a variety of human diseases from both a biological and therapeutic standpoint.

Prostaglandin E2 and its cognate EP receptors control human adult articular cartilage homeostasis and are linked to the pathophysiology of osteoarthritis

OBJECTIVE

To elucidate the pathophysiologic links between prostaglandin E(2) (PGE(2)) and osteoarthritis (OA) by characterizing the catabolic effects of PGE(2) and its unique receptors in human adult articular chondrocytes.

METHODS

Human adult articular chondrocytes were cultured in monolayer or alginate beads with and without PGE(2) and/or agonists of EP receptors, antagonists of EP receptors, and cytokines. Cell survival, proliferation, and total proteoglycan synthesis and accumulation were measured in alginate beads. Chondrocyte-related gene expression and phosphatidylinositol 3-kinase/Akt signaling were assessed by real-time reverse transcription-polymerase chain reaction and Western blotting, respectively, using a monolayer cell culture model.

RESULTS

Stimulation of human articular chondrocytes with PGE(2) through the EP2 receptor suppressed proteoglycan accumulation and synthesis, suppressed aggrecan gene expression, did not appreciably affect expression of matrix-degrading enzymes, and decreased the type II collagen:type I collagen ratio. EP2 and EP4 receptors were expressed at higher levels in knee cartilage than in ankle cartilage and in a grade-dependent manner. PGE(2) titration combined with interleukin-1 (IL-1) synergistically accelerated expression of pain-associated molecules such as inducible nitric oxide synthase and IL-6. Finally, stimulation with exogenous PGE(2) or an EP2 receptor-specific agonist inhibited activation of Akt that was induced by insulin-like growth factor 1.

CONCLUSION

PGE(2) exerts an antianabolic effect on human adult articular cartilage in vitro, and EP2 and EP4 receptor antagonists may represent effective therapeutic agents for the treatment of OA.

Telomerase transduced osteoarthritis fibroblast-like synoviocytes display a distinct gene expression profile

OBJECTIVE

To examine the differential gene expression in telomerase transduced osteoarthritis fibroblast-like synoviocytes (hTERT-OA 13A FLS) and telomerase transduced rheumatoid arthritis FLS (hTERT-RA 516 FLS) and test the hypothesis that longterm culture of hTERT-OA 13A FLS display a disease-specific gene expression profile.

METHODS

Gene expression in passage 8 hTERT-OA 13A FLS and passage 8 hTERT-RA 516 FLS were compared using microarray assays. Differential expression of selected genes was further examined by reverse transcription-polymerase chain reaction (RT-PCR). After continuous expansion in culture for an additional 4 months, gene expression in the longterm cultures of hTERT-OA 13A FLS and hTERT-RA 516 FLS was again examined with microarray and real-time RT-PCR.

RESULTS

hTERT-OA 13A FLS displayed a distinct gene expression profile. While hTERT-RA 516 FLS expressedADAMTS1, ADAMTS3, ADAMTS5, and several carboxypeptidases, hTERT-OA 13A FLS expressed matrix metalloproteinase (MMP)1, MMP3, and several cathepsins at higher levels. Numerous genes classified in the immune response, lipid transport/catabolism, and phosphate transport biological processes were also expressed at higher levels in hTERT-OA 13A FLS. In contrast, numerous genes classified in the positive regulation of cell proliferation, anti-apoptosis, and angiogenesis biological processes were expressed at higher levels in hTERT-RA 516 FLS. Further, of the recently proposed 21 candidate synovial biomarkers of OA, 12 (57%) were detected in our study.

CONCLUSION

The findings indicate that OA FLS may not be a passive bystander in OA and that telomerase transduced OA FLS offer an alternative tool for the study of synovial disease markers and for the identification of new therapeutic targets for OA therapy.

Protective effects of total fraction of avocado/soybean unsaponifiables on the structural changes in experimental dog osteoarthritis: inhibition of nitric oxide synthase and matrix metalloproteinase-13

INTRODUCTION

The aims of this study were, first, to investigate the in vivo effects of treatment with avocado/soybean unsaponifiables on the development of osteoarthritic structural changes in the anterior cruciate ligament dog model and, second, to explore their mode of action.

METHODS

Osteoarthritis was induced by anterior cruciate ligament transection of the right knee in crossbred dogs. There were two treatment groups (n = 8 dogs/group), in which the animals received either placebo or avocado/soybean unsaponifiables (10 mg/kg per day), which were given orally for the entire duration of the study (8 weeks). We conducted macroscopic and histomorphological analyses of cartilage and subchondral bone of the femoral condyles and/or tibial plateaus. We also conducted immunohistochemical analyses in cartilage for the following antigens: inducible nitric oxide synthase, matrix metalloproteinase (MMP)-1, MMP-13, a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS)4 and ADAMTS5.

RESULTS

The size of macroscopic lesions on the tibial plateaus was decreased (P = 0.04) in dogs treated with the avocado/soybean unsaponifiables. Histologically, in these animals the severity of cartilage lesions on both tibial plateaus and femoral condyles, and the cellular infiltration in synovium were significantly decreased (P = 0.0002 and P = 0.04, respectively). Treatment with avocado/soybean unsaponifiables also reduced loss of subchondral bone volume (P < 0.05) and calcified cartilage thickness (P = 0.01) compared with placebo. Immunohistochemical analysis of cartilage revealed that avocado/soybean unsaponifiables significantly reduced the level of inducible nitric oxide synthase (P < 0.05) and MMP-13 (P = 0.01) in cartilage.

CONCLUSIONS

This study demonstrates that treatment with avocado/soybean unsaponifiables can reduce the development of early osteoarthritic cartilage and subchondral bone lesions in the anterior cruciate ligament dog model of osteoarthritis. This effect appears to be mediated through the inhibition of inducible nitric oxide synthase and MMP-13, which are key mediators of the structural changes that take place in osteoarthritis.

Modulation of xylosyltransferase I expression provides a mechanism regulating glycosaminoglycan chain synthesis during cartilage destruction and repair

Osteoarthritis and rheumatoid arthritis are characterized by loss of proteoglycans (PGs) and their glycosaminoglycan (GAG) chains that are essential for cartilage function. Here, we investigated the role of glycosyltransferases (GTs) responsible for PG-GAG chain assembly during joint cartilage destruction and repair processes. At various times after antigen-induced arthritis (AIA) and papain-induced cartilage repair in rats, PG synthesis and deposition, expression of GTs, and GAG chain composition were analyzed. Our data showed that expression of the GT xylosyltransferase I (XT-I) gene initiating PG-GAG chain synthesis was significantly reduced in AIA rat cartilage and was associated with a decrease in PG synthesis. Interestingly, interleukin-1beta, the main proinflammatory cytokine incriminated in joint diseases, down-regulated the XT-I gene expression with a concomitant decrease in PG synthesis in rat cartilage explants ex vivo. However, cartilage from papain-injected rat knees showed up-regulation of XT-I gene expression and increased PG synthesis at early stages of cartilage repair, a process associated with up-regulation of TGF-beta1 gene expression and mediated by p38 mitogen-activated protein kinase activation. Consistently, silencing of XT-I expression by intraarticular injection of XT-I shRNA in rat knees prevented cartilage repair by decreasing PG synthesis and content. These findings show that GTs play a key role in the loss of PG-GAGs in joint diseases and identify novel targets for stimulating cartilage repair.

The effects of ketorolac tromethamine and baicalein on the levels of inflammatory factors in human synoviocytes

This study examined the effects of ketorolac tromethamine (KT) and baicalein (BE) on the levels of inflammatory factors in human synoviocytes. The fibroblast-like synoviocytes (FLS) cells were used to determine the possible regulatory effects of KT and BE (KTBE) on the levels of inflammatory factors in FLS cells. In addition, the levels of TNF-alpha, IL-6, and IL-1beta mRNA expression in FLS cells induced by a TNF-alpha and IL-1beta co-treatment were largely inhibited by a KTBE treatment. The level of FLS cells proliferation was increased by IL-1beta and TNF-alpha, and strongly inhibited by KTBE treatment. The production of oxygen species (ROS) was inhibited by KTBE in FLS cells. KTBE appears to regulate the levels of mRNA that are important for regulating RA progression.

The Development of Novel Therapies for Rheumatoid Arthritis

BACKGROUND: Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory disease that affects approximately 0.5 to 1 percent of the adults worldwide and commonly results in joint destruction and significant impairment in the quality of life. RA is considered as an autoimmune disease with unknown etiology. Many pathogenic pathways of RA have been revealed recently, which led to development of various novel therapies. OBJECTIVE: The current treatments of RA include 4 categories: non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, non-biologic disease-modifying anti-rheumatic drugs (DMARDs) and biologic DMARDs. In this review, we will discuss some of the most recent development in antirheumatic therapies. METHODS: Using SciFinder Scholar and PubMed as main searching tools, we evaluated various newly developed therapies for RA. Under each drug category, emphases are placed on the mode of action, limitation of the drugs and new drug candidates from the patents search. Those well-established therapies will only be reviewed briefly. CONCLUSION: During the past 20 years, most of the development of new therapies is in DMARDs, especially biological DMARDs. With the discovery of new pathways and the application of drug delivery strategies, more growth is anticipated in this research field.

Neutralizing IL-21 and IL-15 inhibits pro-inflammatory cytokine production in rheumatoid arthritis

Interleukin IL-21 and IL-15 belong to the common gamma-chain receptor family. IL-15 represents a novel therapeutic target in rheumatoid arthritis (RA), whereas less is known about the role of IL-21 in human inflammatory diseases. We have analysed the effects of blocking IL-21 and IL-15 on spontaneous production of pro-inflammatory cytokines in RA synovial cell cultures. RA synovial membrane cells were cultured in the presence of an IL-21R-Fc chimera or a neutralizing IL-15 antibody and production of tumour necrosis factor (TNF)alpha, IL-6 and IL-1beta was measured by enzyme-linked immunosorbent assay (ELISA). Expression of IL-21 and IL-15 in RA synovium was measured by RT-PCR and ELISA. mRNA for IL-21 and IL-21R was detected in the culture cell lysates. Protein for IL-15 was found at detectable levels in the cell lysates. Both the IL-21R-Fc chimera and anti-IL-15 antibody inhibited cytokine release, although substantially more IL-21R-Fc was needed. IL-21R-Fc at the highest dose (100 microg/ml) significantly reduced TNFalpha production by 50%, IL-6 by 57% and IL-1beta by 81%. Anti-IL-15 antibody (5 microg/ml) significantly inhibited TNFalpha release by 51%, IL-6 by 37% and IL-1beta by 82% in line with previous published observations. The data confirm that IL-15 plays a role in RA and suggests that IL-21 is also involved in driving the pro-inflammatory cytokine response in RA.

Proteinases in the joint: clinical relevance of proteinases in joint destruction

Proteinases are involved in essential steps in cartilage and bone homeostasis. Consequently, efforts have been made to establish their potential role in the pathology of rheumatic conditions such as rheumatoid arthritis, osteoarthritis and spondyloarthritis. Matrix metalloproteinases (MMPs) are sensitive markers of disease severity and response to treatment, and therefore they have potential in the assessment of rheumatic diseases. Despite disappointing early results with synthetic inhibitors of MMPs, there is still much scope for developing effective and safe MMPs inhibitors, and consequently to deliver new options to inhibit joint destruction.

The effect of electrical fields on gene and protein expression in human osteoarthritic cartilage explants

BACKGROUND

The destruction of cartilage in patients with osteoarthritis is a consequence of an imbalance between matrix synthesis and degradation. The purpose of the present study was to determine the effects of electrical stimulation on these processes in full-thickness osteoarthritic adult human articular cartilage explants.

METHODS

Full-thickness articular cartilage explants from osteoarthritic adult human knee joints were cultured in the absence or presence of interleukin-1beta (IL-1beta) and in the absence or presence of a specifically defined capacitively coupled electrical signal for seven or fourteen days. Total collagen and proteoglycan production were assessed by means of hydroxyproline and hexosamine analyses, respectively. Quantitative real-time polymerase chain reaction assays were used to measure mRNA expression levels of aggrecan, type-II collagen, collagenase-1 (MMP-1), collagenase-3 (MMP-13), stromelysin-1 (MMP-3), aggrecanase-1 (ADAM-TS4), and aggrecanase-2 (ADAM-TS5).

RESULTS

Electrical stimulation of cultured explants for seven or fourteen days resulted in significant increases (p < 0.007) in proteoglycan and collagen production and a highly significant upregulation (p <or= 0.005) of aggrecan and type-II collagen mRNA expression. This occurred even in the presence of IL-1beta. In the absence of IL-1beta, the expression of metalloproteinases was at barely detectable levels in these explants. Treatment with IL-1beta led to the significant upregulation of metalloproteinase expression (p < 0.03), but simultaneous administration of the capacitively coupled electrical signal dramatically inhibited this stimulation.

CONCLUSIONS

The data show that, even in the presence of IL-1beta, a specific, defined capacitively coupled electrical signal can result in significant upregulation of cartilage matrix protein expression and production while simultaneously significantly attenuating the upregulation of metalloproteinase expression. These results support the contention that delivery of a specific, defined electrical field to articular cartilage could result in matrix preservation.

Inhibition of integrative repair of the meniscus following acute exposure to interleukin-1 in vitro

Damage or loss of the meniscus is associated with progressive osteoarthritic degeneration of the knee joint. Injured and degenerative joints are characterized by elevated levels of the pro-inflammatory cytokine interleukin-1 (IL-1), which with prolonged exposure can induce catabolic and anti-anabolic activities that inhibit tissue repair. We used an in vitro model system to examine the hypotheses that acute exposure to IL-1 inhibits meniscal repair, and that an IL-1-mediated increase in matrix metalloproteinase (MMP) activity is associated with the inhibition of repair. Integrative tissue repair was studied between concentric explants of porcine medial menisci that were treated with IL-1alpha acutely (100 pg/mL for 1 or 3 days) or chronically (100 pg/mL for entire culture duration). After 14 and 28 days in culture, biomechanical testing, cell viability, and histology were performed to assess meniscal repair. Total specific MMP activity in the culture media was measured using a quenched fluorescent substrate. As little as 1 day of IL-1 exposure significantly reduced shear strength, cell accumulation, and tissue repair compared to controls. IL-1 exposure for 1 or 3 days significantly increased MMP activity that subsided by day 9. With chronic IL-1 exposure, MMP activity remained elevated for the duration of culture and was negatively correlated with repair strength. Our study shows that short-term exposure to physiologically relevant concentrations of IL-1 significantly reduces meniscal repair in vitro, and thus may potentially inhibit the intrinsic repair response in vivo. The suppression of IL-1 or MMP expression and/or activity warrant investigation as potential strategies for promoting meniscal repair.

Activation of proteinase-activated receptor 2 in human osteoarthritic cartilage upregulates catabolic and proinflammatory pathways capable of inducing cartilage degradation: a basic science study

Proteinase-activated receptors (PARs) belong to a family of G protein-coupled receptors. PARs are activated by a serine-dependent cleavage generating a tethered activating ligand. PAR-2 was shown to be involved in inflammatory pathways. We investigated the in situ levels and modulation of PAR-2 in human normal and osteoarthritis (OA) cartilage/chondrocytes. Furthermore, we evaluated the role of PAR-2 on the synthesis of the major catabolic factors in OA cartilage, including metalloproteinase (MMP)-1 and MMP-13 and the inflammatory mediator cyclooxygenase 2 (COX-2), as well as the PAR-2-activated signalling pathways in OA chondrocytes. PAR-2 expression was determined using real-time reverse transcription-polymerase chain reaction and protein levels by immunohistochemistry in normal and OA cartilage. Protein modulation was investigated in OA cartilage explants treated with a specific PAR-2-activating peptide (PAR-2-AP), SLIGKV-NH₂ (1 to 400 μM), interleukin 1 beta (IL-1β) (100 pg/mL), tumor necrosis factor-alpha (TNF-α) (5 ng/mL), transforming growth factor-beta-1 (TGF-β1) (10 ng/mL), or the signalling pathway inhibitors of p38 (SB202190), MEK1/2 (mitogen-activated protein kinase kinase) (PD98059), and nuclear factor-kappa B (NF-κB) (SN50), and PAR-2 levels were determined by immunohistochemistry. Signalling pathways were analyzed on OA chondrocytes by Western blot using specific phospho-antibodies against extracellular signal-regulated kinase 1/2 (Erk1/2), p38, JNK (c-jun N-terminal kinase), and NF-κB in the presence or absence of the PAR-2-AP and/or IL-1β. PAR-2-induced MMP and COX-2 levels in cartilage were determined by immunohistochemistry. PAR-2 is produced by human chondrocytes and is significantly upregulated in OA compared with normal chondrocytes (p < 0.04 and p < 0.03, respectively). The receptor levels were significantly upregulated by IL-1β (p < 0.006) and TNF-α (p < 0.002) as well as by the PAR-2-AP at 10, 100, and 400 μM (p < 0.02) and were downregulated by the inhibition of p38. After 48 hours of incubation, PAR-2 activation significantly induced MMP-1 and COX-2 starting at 10 μM (both p < 0.005) and MMP-13 at 100 μM (p < 0.02) as well as the phosphorylation of Erk1/2 and p38 within 5 minutes of incubation (p < 0.03). Though not statistically significant, IL-1β produced an additional effect on the activation of Erk1/2 and p38. This study documents, for the first time, functional consequences of PAR-2 activation in human OA cartilage, identifies p38 as the major signalling pathway regulating its synthesis, and demonstrates that specific PAR-2 activation induces Erk1/2 and p38 in OA chondrocytes. These results suggest PAR-2 as a potential new therapeutic target for the treatment of OA.

Serum amyloid A-induced IL-6 production by rheumatoid synoviocytes

In this study, we investigated the role of serum amyloid A protein (SAA) in the production of interleukin-6 (IL-6) using rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS). Recombinant SAA stimulation induced the production of pro-inflammatory cytokine, IL-6, from RA-FLS. The signaling events induced by SAA included the activation of the mitogen-activated protein kineases, p38 and JNK1/2 and the activation of nuclear factor-kappa B (NF-kappaB). Inhibitor studies have shown SAA-induced IL-6 production to be down-regulated by NF-kappaB inhibition and partially inhibited by p38 or JNK inhibitors. Our findings demonstrate that SAA is a significant inducer of IL-6, which is critically involved in RA pathogenesis.

Activity and potential role of licofelone in the management of osteoarthritis

Osteoarthritis is the most common form of arthritis. It is a progressive joint disease associated with aging. It may be found in the knees, hips, or other joints. It is estimated that costs associated with osteoarthritis exceed 2% of the gross national product in developed countries. Nonsteroidal anti-inflammatory drugs (NSAIDs) are a mainstay in the treatment of inflammatory disease and are among the most widely used drugs worldwide. The main limitation in using NSAIDs consists in their side-effects, including gastrointestinal ulcerogenic activity and bronchospasm. The mechanism of action of these drugs is attributed to the inhibition of cyclooxygenase (COX), and, consequently, the conversion of arachidonic acid into prostaglandins. It is hypothesized that the undesirable side-effects of NSAIDs are due to the inhibition of COX-1 (constitutive isoform), whereas the beneficial effects are related to the inhibition of COX-2 (inducible isoform). Arachidonic acid can also be converted to leukotrienes (LTs) by the action of 5-lipoxygenase (5-LOX). Licofelone, a LOX/COX competitive inhibitor, decreases the production of proinflammatory leukotrienes and prostaglandins (which are involved in the pathophysiology of osteoarthritis and in gastrointestinal (GI) damage induced by NSAIDs) and has the potential to combine good analgesic and anti-inflammatory effects with excellent GI tolerability. Preliminary data with this drug seem promising, but further well-designed clinical trials of this agent in the elderly will be necessary before a final evaluation is possible.

Transforming growth factor alpha suppression of articular chondrocyte phenotype and Sox9 expression in a rat model of osteoarthritis

OBJECTIVE

To define the roles of transforming growth factor alpha (TGFalpha) in cartilage degradation.

METHODS

Primary rat articular chondrocytes and articular osteochondral explants were cultured with TGFalpha to assess the effects of TGFalpha on chondrocyte physiology and phenotype.

RESULTS

TGFalpha altered chondrocyte morphology through reorganization of the actin cytoskeleton and formation of stress fibers. Expression of anabolic genes, including aggrecan, type II collagen, and cartilage link protein, was reduced in response to TGFalpha. Proliferation of chondrocytes and formation of articular chondrocyte clusters was stimulated by TGFalpha. Expression of matrix metalloproteinase 13 and cathepsin C was increased by TGFalpha. We demonstrated the down-regulation of Sox9 messenger RNA and protein levels by TGFalpha. This was associated with reduced levels of phosphorylated and total SOX9 in cartilage explants upon TGFalpha treatment. In contrast, another growth factor identified in our microarrays, Kitl, had no effects on the chondrocyte parameters tested. To examine correlations between the increased levels of TGFalpha in experimental knee osteoarthritis (OA) with the levels of TGFalpha in humans with knee OA, a microarray analysis of mRNA from 13 normal and 12 late-stage OA cartilage samples was performed. Seven OA samples showed TGFA mRNA levels similar to those in the normal controls, but expression was markedly increased in the other 5 OA samples. These data confirm that TGFA transcript levels are increased in a subset of patients with OA.

CONCLUSION

This study adds TGFalpha to the list of dysregulated cytokines present in degrading cartilage in OA. Since TGFalpha inhibits articular chondrocyte anabolic capacity, increases catabolic factors, and contributes to the development of chondrocyte clusters, TGFalpha may be a potential target for therapeutic strategies in the treatment of OA.

Basic fibroblast growth factor activates the MAPK and NFkappaB pathways that converge on Elk-1 to control production of matrix metalloproteinase-13 by human adult articular chondrocytes

The pathology of joint destruction is associated with elevated production of basic fibroblast growth factor (bFGF) and matrix metalloproteinase-13 (MMP-13). In osteoarthritic joint disease, expression of bFGF and MMP-13 in chondrocytes and their release into the synovial fluid are significantly increased. We have previously found that the capacity for cartilage repair in human adult articular chondrocytes is severely compromised by minimal exposure to bFGF because bFGF reduces responsiveness to bone morphogenetic protein-7 and insulin-like growth factor-1 and induces MMP-13 through protein kinase Cdelta-dependent activation of multiple mitogen-activated protein kinase (MAPK) signaling pathways. Here we show using biochemical and molecular approaches that transcription factor Elk-1, a direct downstream target of MAPK, is a critical transcriptional activator of of MMP-13 by bFGF in human articular chondrocytes. We also provide evidence that Elk-1 is a direct target of NFkappaB and induces MMP-13 expression upon activation of the NFkappaB signaling pathway. Taken together, our results suggest that elevated expression of MMP-13 occurs through Elk-1 activation of both MAPK and NFkappaB signaling pathways, thus revealing a two-pronged biological mechanism by which bFGF controls the production of catabolic enzymes that are associated with excessive degradation of the cartilage matrix in degenerative joint diseases such as osteoarthritis.

Matrix metalloproteases: underutilized targets for drug delivery

Pathophysiological molecules in the extracellular environment offer excellent targets that can be exploited for designing drug targeting systems. Matrix metalloproteases (MMPs) are a family of extracellular proteolytic enzymes that are characterized by their overexpression or overactivity in several pathologies. Over the last two decades, the MMP literature reveals heightened interest in the research involving MMP biology, pathology and targeting. This review describes various strategies that have been designed to utilize MMPs for targeting therapeutic entities. Key factors that need to be considered in the successful design of such systems have been identified based on the analyses of these strategies. Development of targeted drug delivery using MMPs has been steadily pursued; however, drug delivery efforts using these targets need to be intensified and focused to realize the clinical application of the fast developing fundamental MMP research.

Angiogenesis and chronic inflammation: cause or consequence?

Evidence has been gathered regarding the association between angiogenesis and inflammation in pathological situations. These two phenomena have long been coupled together in many chronic inflammatory disorders with distinct etiopathogenic origin, including psoriasis, rheumatoid arthritis, Crohn's disease, diabetes, and cancer. Lately, this concept has further been substantiated by the finding that several previously established non-inflammatory disorders, such as osteoarthritis and obesity, display both inflammation and angiogenesis in an exacerbated manner. In addition, the interplay between inflammatory cells, endothelial cells and fibroblasts in chronic inflammation sites, together with the fact that inflammation and angiogenesis can actually be triggered by the same molecular events, further strengthen this association. Therefore, elucidating the underlying cellular and molecular mechanisms that gather together the two processes is mandatory in order to understand their synergistic effect, and to develop new therapeutic approaches for the management of these disorders that cause a great deal of discomfort, disability, and in some cases death.

Regulation of matrix metalloproteinase gene expression by a retinoid X receptor-specific ligand

OBJECTIVE

To evaluate the effects of LG100268 (LG268), a synthetic ligand for the nuclear hormone receptor retinoid X receptor, on the expression of matrix metalloproteinase 1 (MMP-1) and MMP-13 induced by proinflammatory cytokines in a chondrocyte model.

METHODS

SW-1353 human chondrosarcoma cells were used to study the effects of LG268 on interleukin-1beta (IL-1beta)-stimulated MMP production and collagen degradation. Gene expression was determined by quantitative real-time reverse transcription-polymerase chain reaction, and protein levels were determined by Western blot analysis. Collagen degradation was determined by an in vitro matrix destruction assay. The effects of LG268 on nuclear protein binding and histone acetylation were determined by electrophoretic mobility shift assay and chromatin immunoprecipitation assay, respectively.

RESULTS

LG268 treatment specifically antagonized the IL-1beta-mediated induction of MMP-1 and MMP-13 heterogeneous nuclear RNA, messenger RNA, and protein. The inhibitory effect of LG268 was found to be due to a decrease in the rate of MMP-1 and MMP-13 transcription. LG268 treatment also prevented the in vitro degradation of a type I collagen matrix by IL-1beta-treated SW-1353 cells. The inhibitory effect of LG268 on MMP-1 and MMP-13 transcription appears to be mediated, at least in part, through modulation of histone modification in regions of the MMP-1 and MMP-13 promoters that contain binding sites for activator protein 1 transcription factors.

CONCLUSION

These data indicate that LG268 treatment selectively inhibits inflammatory cytokine-induced production of MMP-1 and MMP-13 at the level of gene transcription and blocks collagen destruction by proinflammatory cytokine-stimulated chondrocytic cells. This study is among the first to describe how rexinoids affect gene expression, and the findings suggest that the rexinoid class of compounds may have a future role in preventing the irreversible collagen destruction seen in the arthritides.

Macrophage migration inhibitory factor: a mediator of matrix metalloproteinase-2 production in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by destruction of bone and cartilage, which is mediated, in part, by synovial fibroblasts. Matrix metalloproteinases (MMPs) are a large family of proteolytic enzymes responsible for matrix degradation. Macrophage migration inhibitory factor (MIF) is a cytokine that induces the production of a large number of proinflammatory molecules and has an important role in the pathogenesis of RA by promoting inflammation and angiogenesis. In the present study, we determined the role of MIF in RA synovial fibroblast MMP production and the underlying signaling mechanisms. We found that MIF induces RA synovial fibroblast MMP-2 expression in a time-dependent and concentration-dependent manner. To elucidate the role of MIF in MMP-2 production, we produced zymosan-induced arthritis (ZIA) in MIF gene-deficient and wild-type mice. We found that MMP-2 protein levels were significantly decreased in MIF gene-deficient compared with wild-type mice joint homogenates. The expression of MMP-2 in ZIA was evaluated by immunohistochemistry (IHC). IHC revealed that MMP-2 is highly expressed in wild-type compared with MIF gene-deficient mice ZIA joints. Interestingly, synovial lining cells, endothelial cells, and sublining nonlymphoid mononuclear cells expressed MMP-2 in the ZIA synovium. Consistent with these results, in methylated BSA (mBSA) antigen-induced arthritis (AIA), a model of RA, enhanced MMP-2 expression was also observed in wild-type compared with MIF gene-deficient mice joints. To elucidate the signaling mechanisms in MIF-induced MMP-2 upregulation, RA synovial fibroblasts were stimulated with MIF in the presence of signaling inhibitors. We found that MIF-induced RA synovial fibroblast MMP-2 upregulation required the protein kinase C (PKC), c-jun N-terminal kinase (JNK), and Src signaling pathways. We studied the expression of MMP-2 in the presence of PKC isoform-specific inhibitors and found that the PKCdelta inhibitor rottlerin inhibits MIF-induced RA synovial fibroblast MMP-2 production. Consistent with these results, MIF induced phosphorylation of JNK, PKCdelta, and c-jun. These results indicate a potential novel role for MIF in tissue destruction in RA.

Dual effects of the membrane-anchored MMP regulator RECK on chondrogenic differentiation of ATDC5 cells

Extracellular matrix (ECM) undergoes continuous remodeling during mammalian development. Although involvement of matrix metalloproteinases (MMPs) in ECM degradation has been well documented, how this process is regulated to allow proper ECM accumulation remains unclear. We previously showed the involvement of a membrane-anchored MMP regulator, RECK (reversion-inducing cysteine-rich protein with Kazal motifs), in vascular development in mice. Here we report that Reck mRNA can be detected in developing cartilage in E13.5 approximately 16.5 mouse embryos and is progressively upregulated during differentiation of a chondrogenic cell line ATDC5 in vitro. In the early phase of ATDC5 differentiation, RECK expression stays low, multiple MMPs are upregulated, and there is ECM degradation at the sites of cellular condensation. In the later phase, RECK is upregulated inside the expanding cartilaginous nodules where type II collagen is accumulated while active ECM degradation persists along the rim of the nodules. Constitutive RECK expression suppressed initial cellular condensation, whereas RECK knockdown suppressed the later ECM accumulation in the cartilaginous nodules. These results suggest that RECK expression at the right place (in the core of the nodules) and at the right time (only in the later phase) is important for proper chondrogenesis and that RECK, together with MMPs, plays a crucial role in regulating dynamic processes of tissue morphogenesis.

Regulatory polymorphisms in extracellular matrix protease genes and susceptibility to rheumatoid arthritis: a case-control study

Many extracellular matrix (ECM) proteases seem to be important in rheumatoid arthritis (RA) and regulation of their transcription levels is a critical mechanism for controlling their activity. We have investigated, therefore, whether the best-characterized single nucleotide polymorphisms (SNPs) affecting transcription of the ECM proteases that have been related with joint pathology are associated with RA susceptibility. Nine SNPs in eight genes were selected by bibliographic search, including SNPs in the genes encoding matrix metalloproteinase (MMP)1, MMP2, MMP3, MMP7, MMP9, MMP13, plasminogen activator, tissue type (PLAT) and PAI-1. They were studied in a case-control setting that included 550 RA patients and 652 controls of Spanish ancestry from a single center. Genotyping was performed by single-base extension. Only two of the nine SNPs showed significant association with RA susceptibility. RA patients showed increased frequencies of the -7351 T allele of the gene encoding PLAT (36.4% versus 32.1% in controls, p = 0.026) and the -1306 T allele of the gene encoding MMP2 (24.5% versus 20.3% in controls, p = 0.013). These two alleles seemed to cooperate according to an additive model with respect to increased RA susceptibility (p = 0.004), and they were the low-expression alleles of the respective SNPs in a PLAT enhancer and the MMP2 promoter. These findings are in agreement with previous data suggesting that these two ECM proteases have a protective role in RA pathology. Confirmation of these associations will be needed to support these hypotheses. The remaining SNPs did not show association, either individually or collectively. Therefore, although regulatory SNPs in ECM proteases did not show any major effect on RA susceptibility, it was possible to find modest associations that, if replicated, will have interesting implications in the understanding of RA pathology.

Functional characterization of an orphan nuclear receptor, Rev-ErbAalpha, in chondrocytes and its potential role in osteoarthritis

OBJECTIVE

To evaluate the expression and function of the orphan nuclear receptor Rev-ErbAalpha in articular cartilage and to investigate its role in osteoarthritis (OA).

METHODS

Expression of Rev-ErbAalpha was analyzed at both the messenger RNA and protein levels in human and bovine articular cartilage and chondrocytes by real-time polymerase chain reaction (TaqMan) and immunocytochemical techniques. The effects of cartilage catabolic and anabolic agents on the expression of Rev-ErbAalpha were evaluated by TaqMan analysis. Overexpression was achieved by either adenoviral transduction or treatment with a peroxisome proliferator-activated receptor alpha agonist, whereas expression was suppressed by antisense oligonucleotides.

RESULTS

Among the 48 known nuclear receptors, Rev-ErbAalpha was found to be the most highly expressed in OA cartilage. It is known to function as a transcription repressor. Treatment of articular chondrocytes with known catabolic agents resulted in the induction of Rev-ErbAalpha, whereas stimulation with anabolic agents led to a decrease in expression. Overexpression of the nuclear receptor was associated with an increase in the expression of matrix-degrading enzymes such as matrix metalloproteinase 13 and aggrecanase. In contrast, a decrease in Rev-ErbAalpha expression led to a concomitant reduction in the activity of matrix-degrading enzymes.

CONCLUSION

This study is the first to demonstrate that Rev-ErbAalpha is highly expressed in OA articular chondrocytes and that its expression is modulated by known cartilage catabolic and anabolic stimuli. We also demonstrated that modulation of Rev-ErbAalpha expression in chondrocytes may be a novel means of regulating the expression and production of multiple matrix-degrading enzymes. These observations suggest that Rev-ErbAalpha may be a novel therapeutic target for OA.

Inhibitory effect of chitooligosaccharides on matrix metalloproteinase-9 in human fibrosarcoma cells (HT1080)

Matrix metalloproteinase-9 (MMP-9) has gelatinase activity and plays an important role in cancer invasion and metastasis. Therefore, inhibition of specific types of MMPs including MMP-9 has become an attractive target for therapeutic intervention. The aim of this study was to investigate the effect of chitooligosaccharides (COS) on activity and expression of MMP-9 in HT1080 cells. The inhibitory effect of COS with different molecular masses was examined by gelatin zymography, reverse transcriptase-polymerase chain reaction (RT-PCR), gene reporter assay, and Western blot analysis. MMP-9 inhibition in the presence of COS was clearly observed in gelatin zymography. Specifically, 1- to 3-kDa COS (COS-I) exhibited the highest inhibitory effect on MMP-9 activity in HT1080 cells among tested molecular mass fractions. It was also found that COS-I was capable of inhibiting both gene and protein expression of MMP-9 (P<0.01). These results suggest that low molecular mass COS can be considered as a potent inhibitor of MMP-9.

Expression of genes for gelatinases and tissue inhibitors of metalloproteinases in periodontal tissues during orthodontic tooth movement

Orthodontic tooth movement progresses by a combination of periodontal ligament (PDL) tissue and alveolar bone remodeling processes. Besides the remodeling of alveolar bone around the moving teeth, the major extracellular matrix (ECM) components of PDLs, collagens, are degenerated, degraded, and restructured. Matrix metalloproteinases (MMPs) and their specific inhibitors, tissue inhibitors of metalloproteinases (TIMPs), act in a co-ordinated fashion to regulate the remodeling of periodontal tissues. We hypothesized that the expression levels of the genes for MMP-2, MMP-9, and TIMPs 1-3 are increased transiently in the periodontal tissue during orthodontic tooth movement. To test this hypothesis, we employed an animal model of tooth movement using rats, as well as in situ hybridization to analyze the expression levels of Mmp-2, Mmp-9, and Timps 1-3. The expression levels of these genes increased transiently in cells of periodontal tissues, which include cementoblasts, fibroblasts, osteoblasts, and osteoclasts, at the compression side of the moving teeth. The transient increases in gene expression at the tension side were mainly limited to osteoblasts and cementoblasts. In conclusion, the expression levels of Mmp-2, Mmp-9, and Timps 1-3 increase transiently during orthodontic tooth movement at both the tension and compression sides. The expression of these genes is regulated differentially in the periodontal tissue of the tension side and compression side. This altered pattern of gene expression may determine the rate and extent of remodeling of the collagenous ECM in periodontal tissues during orthodontic tooth movement.